Fagopyrum dibotrys is one of the innumerable plants used in Chinese traditional medicine. The whole plant, particularly the rhizome, is used as a medicament, allegedly having a wide range of beneficial effects, including antitumour activity.
Zhang Wen-Jie et al., Acta Botanica Yunnanica, 1994, 16, 354-356 separated and identified a number of phenolic constituents. The compound obtained in highest yield (0.19%) was termed procyanidin B-2 and was assigned the formula (1) (see FIG. 1). This compound has 5 asymmetric centres (asterisked in FIG. 1), so potentially there are 32 stereoisomers. No information is available about which isomer(s) is/are present in the isolated material. They are 5,7,3′,4′-tetrahydroxy flavon-3-1 C4-C8 dimers. Such a dimer or dimers was previously isolated from avocado seed (T. A. Geissmann et al. Phytochem., 1965, 4, 359-368).